CN1341084A - Calcined gypsum hydration enhaucing additives - Google Patents
Calcined gypsum hydration enhaucing additives Download PDFInfo
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- CN1341084A CN1341084A CN00804170A CN00804170A CN1341084A CN 1341084 A CN1341084 A CN 1341084A CN 00804170 A CN00804170 A CN 00804170A CN 00804170 A CN00804170 A CN 00804170A CN 1341084 A CN1341084 A CN 1341084A
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/14—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing calcium sulfate cements
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B22/00—Use of inorganic materials as active ingredients for mortars, concrete or artificial stone, e.g. accelerators, shrinkage compensating agents
- C04B22/08—Acids or salts thereof
- C04B22/14—Acids or salts thereof containing sulfur in the anion, e.g. sulfides
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
- C04B2103/10—Accelerators; Activators
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Abstract
An additive for accelerating the setting reaction of gypsum products is disclosed. It comprises a gypsum accelerator combined with a bisulfate salt. The gypsum accelerator is calcium sulfate dihydrate. The accelerator may optionally be ground with a sugar, a starch and/or boric acid. A process utilizing this additive combination is also disclosed. The bisulfate salt is most advantageously prewet with a portion of the calcium sulfate hemihydrate feed before being combined with the gypsum accelerator, water and the remaining portion of the calcium sulfate hemihydrate feed in the main mixer.
Description
Background
The present invention relates to an improved method of hardening calcined gypsum. More particularly, the invention relates to the use of ground gypsum and bisulfate salts in the preparation of gypsum products to reduce set time, reduce water requirements, and reduce drying time.
Gypsum is a very practical and cost effective building material. It is also known as calcium sulfate dihydrate. When the mined calcium sulfate dihydrate is ground, it is also referred to as landplaster. Calcium sulfate hemihydrate is also known as calcined gypsum, stucco, calcium sulfate hemihydrate or molded gypsum. Synthetic gypsum, which is a by-product from a power plant gas desulfurization process, can also be used. On production, the gypsum appears as dihydrate. In this form, two water molecules are associated with each calcium sulfate molecule. To prepare gypsum in the hemihydrate form, the gypsum may be calcined to remove some of the water in the hydrated state, as shown in the following reaction scheme:
many useful gypsum products can be obtained by mixing calcium sulfate hemihydrate and water to form a slurry and casting the resulting slurry product into a desired shape. The slurry product is hardened by reacting the calcium sulfate hemihydrate with sufficient water to convert the hemihydrate to a matrix of interlocking dihydrate crystalline form. In this form of the crystalline matrix, the slurry product becomes strong and has the desired shape. Excess water must then be removed from the product by drying.
The hardening and drying steps are the most time and energy consuming steps in the process of making gypsum products. The setting time of the slurry depends on a number of factors including the age of the calcined gypsum, impurities in the calcined gypsum, surface area, pH, particle size and temperature at the time of mixing. The use of additives or process conditions that reduce the drying time of the gypsum product can result in reduced costs. Lower energy consumption is a result of using lower temperatures or less drying time in the drying stage. Another benefit is the ability to increase line speed and produce more product with the same resources. Reducing the time required for the product to harden may result in a corresponding reduction in production costs.
Many additives are known to increase the rate of hydration reactions. In the later 1950 s, the Bureau of Mines investigated the effect of dissolved substances on the setting time of landplaster. At that time, the mineral agency tested a number of gypsum or water impurities to determine if they caused any acceleration or retardation effects of the hydration reaction. Sulfates and gypsum, including bisulfates, were measured as accelerators at that time. (investigation of Gypsum Hydration Rate: Effect of Small amounts of Dissolved Substances (Hydration-Rate Studies of gypsums: Effects of Small Amountsof dispersed substructures) J.P.Couglin, K.C.Conway, M.F.Koehler and D.F.Barry, Burea of Mines Report of investments 5477, 1959).
Those acid-reactive soluble sulfates that include bisulfate salts are known to accelerate hydration, as indicated in U.S. patent No. 2,216,555 ("King"). However, acidic sulfates also tend to react with impurities in the gypsum, particularly carbonates. King addresses this problem by adding lime and a set retarder to the landplaster to control the decomposition reaction with carbonate. However, the gypsum powder containing excess lime forms a thin layer of soft, unhardened gypsum powder on the surface of the gypsum product, which can result in surface imperfections.
Ground gypsum is also known as a hardening accelerator, particularly when combined with a coating such as starch in U.S. patent No. 3,870,538 or sugar in U.S. patent No. 4,681,644. It is believed that the added dihydrate serves as a "seed" or nucleation site to promote rapid growth of dihydrate crystals in the hydration product slurry. Freshly ground gypsum is very reactive, but its effectiveness decreases rapidly with age. Thus, it is preferred to provide gypsum with a coating that reduces the deactivation of the material over time.
The rate of drying of the gypsum product is determined by two factors. The water demand is the amount of water required to make a slurry of a certain fluidity. The water requirement can be varied by using a rheology modifier corresponding to the gypsum slurry. Additives that increase water demand will prolong the drying time of the gypsum product. Even if the same amount of water is added to the slurry, the additive will alter the rate at which excess water is removed from the formed product. Capillary action draws water from within the crystalline matrix to the surface of the product as excess water evaporates. When the movement of water to the surface is hindered, the drying process becomes slow. If the additive increases the water demand or decreases the rate at which excess water evaporates from the product, it will result in a decrease in line speed, an increase in kiln exposure time, or greater energy consumption from higher kiln temperatures. Either of these circumstances results in higher production costs for the gypsum product.
It is an object of the present invention to provide a more economical method for preparing a hardened gypsum product by reducing the production costs.
It is another object of the present invention to provide an improved accelerator for increasing the rate of set of calcined gypsum.
It is another object of the present invention to reduce the cost of drying gypsum products by reducing the water demand of the slurry.
It is another object of the present invention to provide a more economical method of preparing a set gypsum product which more easily releases excess water and dries quickly.
Brief summary of the invention
The above objects are met or exceeded by the additive composition and method of making a set gypsum product of the present invention, which is characterized by providing a novel additive system to significantly reduce the time and energy required to hydrate and dry the gypsum product.
More specifically, the present invention provides an additive for accelerating the setting reaction of calcined gypsum, the additive comprising a gypsum accelerator in combination with a bisulfate salt. The gypsum accelerator comprises ground calcium sulfate dihydrate. In a preferred embodiment, the gypsum accelerator is treated with a coating agent such as starch, sugar and/or boric acid. In a preferred embodiment, an additive is used in the process, wherein the bisulfate salt and part of the hemihydrate sulfate salt are pre-wetted before mixing in the main mixer.
It has been found that when a bisulfate salt is used with a gypsum accelerator, a surprising effect is observed. The combination of the two components provides a faster rate of hardening than either of the two additives alone. In addition, when used with gypsum accelerators, there is no significant reduction in product strength seen with some of the additives of the prior art. The rapid hardening of the product results in a more efficient preparation of the product. As the product hydrates more rapidly, the speed of the production line will increase, producing more product in the same time. If the production facility is newly built or redesigned, the production line can be built smaller for a given production rate, allowing the saved space to be used for other purposes.
The combination of additives also provides other benefits to the process of setting calcined gypsum that are not seen in the prior art using the additives alone. One significant benefit is the reduction in energy required to dry the product. The additives of the present invention reduce drying time in two ways. First, less water is required to form the slurry because the fluidity of the slurry is improved. This allows less excess water to be present in the product after the hydration reaction is complete. In addition, the excess water present is easier to remove. Therefore, the same amount of product can be prepared by reducing the temperature of the drying kiln, and energy consumption cost is directly saved. The speed of the production line can be increased and more product can be produced for the same amount of fuel consumption. Any of these methods, or combinations thereof, may be used to reduce energy consumption per unit product.
The additives of the present invention may also reduce fouling and prevent the formation of calcium deposits in the mixing device. If the apparatus is kept clean for a longer period of time, the down time for cleaning and maintaining the production line can be reduced. Each of these benefits of the present invention is a more cost effective means of reducing the cost of making gypsum products.
Brief description of the drawings
Figure 1 shows the time required to complete 50% hydration for different sodium bisulfate and gypsum accelerator mixtures.
Figure 2 shows the drying times of gypsum boards for different sodium bisulfate and gypsum accelerator mixtures.
Detailed description of the invention
The invention discloses an additive and a method for preparing a product with calcium sulfate as an essential component, which can accelerate hardening and dry the product. The product is prepared using a calcium sulfate hemihydrate slurry containing a bisulfate salt and a gypsum accelerator.
The bisulfate salt can be any known bisulfate salt. Potassium hydrogen sulfate and sodium hydrogen sulfate are preferred. Sodium bisulfate is most preferred because it is readily available in commercial quantities at reasonable cost. However, other bisulfates, such as potassium bisulfate, ammonium bisulfate, or metal bisulfate, can also be used in the present invention. The salt should be added in an amount of about 0.1 to about 10 pounds per ton of dry calcium sulfate hemihydrate. Preferably, the salt should be present in an amount of about 1 to about 2 pounds per ton of stucco.
The advantage of using bisulfate salts over some other accelerators is that the acceleration in the setting of the landplaster occurs primarily at the final setting of the product or at the final stage of hydration of the product. This has the obvious advantage of being able to easily form the product into a desired shape. For example, when the desired product is gypsum board, if the slurry is concentrated too quickly, it will begin to harden before the board is properly formed. This can result in uneven thickness of the plate, surface wrinkles or edge irregularities. Here, when the accelerator is mainly used at the final stage of the hardening process, there is enough time to properly shape the final product, and the advantage of the accelerated hardening method can be fully embodied.
The second component of this additive is a gypsum accelerator. In its simplest form, the accelerator consists of ground calcium sulfate dihydrate. Mined and ground natural dihydrate known as landplaster is commonly used. However, other sources, such as synthetic gypsum from a gas desulfurization process, may also be used. The gypsum accelerator is present in an amount of from about 3 to about 50 pounds per ton of dry calcium sulfate hemihydrate.
If the gypsum accelerator is not used immediately after grinding, the dihydrate is preferably treated with a coating agent to prevent deactivation over time. Any coating agent having certain properties and known in the art may be used. The coating agent must not delay the setting time of the calcium sulfate hemihydrate to which it is added. The physical properties of the product should also not be impaired by the coating agent. When calcium sulfate hemihydrate and its additives are added to the mixer and water to form a slurry, the coating agent must dissolve to expose active sites of highly fractured crystals. Particularly suitable coating agents include starch, sugar and boric acid or any combination of these compounds. The coating agent may be present in an amount in the range of about 5% to about 25% based on the weight of the dihydrate sulfuric acid feed stream.
When a coating agent is used, the dihydrate crystals and the coating agent may be ground together to reduce the size and at the same time promote an intimate bond between the coating agent and the dihydrate. Any milling device known in the art may be used to mill the material. The preferred milling apparatus is a ball mill. The preparation of a ground calcium sulfate dihydrate and coating agent mixture is known in the art, particularly in U.S. Pat. No. 3,573,947, which is incorporated herein by reference.
In the most preferred embodiment, the coating agent may be melted onto the surface of the dihydrate to maintain the activity of the ground dihydrate for an extended period of time. Sugars such as glucose, sucrose and dextrose are particularly preferred in this embodiment, although any sugar that sufficiently melts at 270 ° F can be used in the gypsum accelerator.
The mixture may then be heated as necessary to melt and caramelize the sugars, allowing them to coat the surface of the ground calcium sulfate dihydrate. This option is preferred if the gypsum accelerator must be stored for later use or transported to another location. The complete coating and caramelization of the sugars serves to seal the surface of the gypsum particles, rendering them less susceptible to aging. When the additive is mixed with water in the slurry product, the caramelised coating dissolves completely, exposing the surface of the highly fractured dihydrate crystals. The dihydrate particles act as "seeds" that promote the growth of crystals as the hemihydrate hydrates to form an interlocking matrix of dihydrate crystals. By heating the coated dihydrate to 250 ° F, excellent accelerator activity can be obtained, but the temperature can be as low as 175 ° F. Temperatures in excess of 270F are generally avoided because they make it difficult to control the moisture content of the accelerator.
The calcium sulfate hemihydrate is added to the process by any method known in the art. Many additives are known to modify or increase the hydration reaction or the properties of the final product. Dry or powdered additives are typically dropped into the dry hemihydrate stream as it moves toward the main mixer. Any method of preparing a constant volumetric flow of dry additive may be used, such as a screw feeder, hopper, or conveyor. The liquid additive may be added to the mixer or pre-mixed with the water to be added to the main mixer.
In another embodiment, the calcium sulfate hemihydrate is pretreated by mixing an amount of calcium sulfate hemihydrate with water. This technique is described in U.S. Pat. No. 4,201,595, which is incorporated herein by reference. All or a portion of the calcium sulfate hemihydrate can be diverted from the main feed stream as a tangential flow. The bisulfate salt is preferably added to the hemihydrate in a tangential flow prior to pretreatment with water. The applicant believes that the prewetted bisulfate is activated by dispersing at least a portion thereof into the tangential flow. This technique results in better dispersion and activity of the bisulfate salt. When the bisulfate salt is pretreated with water, the benefits of the additive combination, such as accelerated hardening, accelerated drying times and reduced water requirements, increase to a greater extent.
Methods of adding water to calcium sulfate hemihydrate and bisulfate salts are known to those skilled in the art. The dry ingredients on the conveyor can simply be sprayed with water. A more preferred method is to use equipment that can blend a high viscosity material such as a bulk mass of moist, granular material. Many commercially available mixers and mixers are suitable. Most preferably, a Scott mixer (Scott Equipment company, Jordan, MN) is used. Water and calcium sulfate hemihydrate can be injected into the mixer simultaneously. Mixing in this way achieves a granulation of the dry components against each other and also disperses the water into the dry components. After mixing, the contents of the mixer are discharged into the primary calcium sulfate hemihydrate feed stream shortly before entering the primary mixer. The pre-wetted tangential flow can also be injected directly into the main mixer.
The amount of water used for pretreatment is about 1% to about 10% by weight of the calcium sulfate hemihydrate in the tangential flow. In a preferred embodiment, water is added to the calcium sulfate hemihydrate mixture in an amount of about 3% to about 5%. The addition of water allows the calcium sulfate hemihydrate crystals to heal. "repair" refers to the fusion of a fracture on a particle due to surface hydration. As a result, the differentiation of the particles upon slurry mixing is reduced. Preferred repair times are in the range of about 1 to about 6 minutes. The repair time is measured from the time the stucco is wet plus all the additives to the time they are introduced into the main mixer. Typically, the gypsum accelerator should be added to the dry hemihydrate stream just prior to its introduction into the main mixer. After all of the calcium sulfate hemihydrate is pre-wetted, a gypsum accelerator is added as the pre-wetted stucco moves from the mixer to the main mixer. Preferably, the wet stucco and the remaining dry hemihydrate are introduced simultaneously to the main mixer.
The total raw mixture, including the stucco, the pre-wet tangential flow, and all additives, is dissolved in an additional amount of water in the main mixer. Sufficient water must be added to convert the calcium sulfate hemihydrate to the dihydrate and to fluidize the slurry sufficiently for its intended use. The use of the additives and methods of the present invention can reduce the water required for gypsum board manufacture to about 50 to about 85 parts by weight per 100 parts by weight of calcined gypsum relative to the normal water demand, i.e., about 85 to about 100 parts by weight per 100 parts by weight of calcined gypsum. The slurry is then formed into a desired product, such as a gypsum board, a mold, etc., and allowed to harden. During hardening, calcium hemihydrate absorbs water due to hydration, converts to an interlocking matrix of dihydrate crystals and hardens.
The final step in the preparation of the product is the removal of excess water. Any suitable method may be used to reduce the excess water and dry the product. The water can be evaporated at room temperature and pressure. All or part of the drying process may be accelerated by using high temperatures, such as kiln drying to accelerate evaporation. For example, the gypsum board may be dried using a kiln until about 90% of the excess water is removed. The remaining water was evaporated under ambient conditions.
Conventional additives may be used in combination with the additive composition or method of the present invention. For example, it is possible to use a composition containing a small amount of a known chemical dispersant or fluidizing agent for calcined gypsum, such as lignin, lignin sulfate, lignin sulfonate and polycondensation products thereof, so that less mixing water is used without interfering with the water reducing effect achieved by the present invention. In this manner, it is possible to achieve the effect of mixing less total water as required, such as about 50 parts by weight of water per 100 parts by weight of calcined gypsum formulated.
Examples 1 to 5
In each experiment, 200g of calcium sulfate hemihydrate (USG, Southardplan) was weighed out and set aside. The appropriate amounts of sodium bisulfate and gypsum accelerator shown in table I were weighed. The gypsum accelerator is composed of 95% landplaster and 5% sugar, which are ground together. Landplaster (USG, Southard plant) used for accelerator contains 96% dihydrate and 4% impurities. After grinding, the coated landplaster is heated to about 250 ° F to melt the sugar on the surface of the landplaster. The calcium sulfate hemihydrate, sodium bisulfate and gypsum accelerator powders are mixed together until all components are thoroughly dispersed. 280ml of 70 ° F water was measured and injected into a Waring mixer with high shear blades. The powdered mixture was soaked for 7 seconds and then mixed at high speed for 7 seconds to form a slurry.
The slurry was poured into the cup, which was then placed in an insulated styrofoam container to reduce heat exchange with the environment. A temperature probe was placed in the middle of the slurry and the temperature was recorded every 5 seconds. Since the hardening reaction is an exothermic reaction, the extent of the reaction can be measured by the rise in temperature. The 50% hydration time was determined as the time to reach an intermediate temperature between the minimum and maximum temperatures recorded in the experiment. The 50% hydration time for different CSA concentrations was recorded as follows:
TABLE I
| Examples | CSA g | Sodium hydrogen sulfate g | 50% hydration time |
| 1 | 1.0 | 0.0 | 6.75 minutes |
| 2 | 0.75 | 0.25 | 5.67 minutes |
| 3 | 0.50 | 0.50 | 6.00 minutes |
| 4 | 0.25 | 0.75 | 6.25 minutes |
| 5 | 0.0 | 1.0 | 10.58 minutes |
In these examples, the benefits of using these two additives are evident. When the total amount of additive is maintained at 1g per 200g of calcium sulfate hemihydrate, the 50% hydration time for all of the mixtures shown is less than the 50% hydration time for either component used alone. Figure 1 graphically represents this data, demonstrating the effect of the combination of these additives on the setting time.
Example 6
Adding the additive of the invention to 1/2' SHEETROCK®In an industrial production line for gypsum wallboard. All amounts specified in this example are based on the amount of 1/2 "board produced at 1000 square feet.
A main feed stream of 1135 pounds of calcined gypsum (USG, Empire plant) was injected into the process stream. A tangential flow of 1% calcium sulfate hemihydrate is diverted from the main feed stream. Sodium bisulfate (Jones-Hamilton) was ground to pass through a 40 mesh screen and added to the tangential flow at a rate of 2 pounds per thousand square feet of finished wallboard. The bisulfate salt was added using an AccuRate powder feeder (AccuRate, inc., Whitewater, WI). The tangential flow containing the bisulfate salt was fed into a Scott mixer (Scott Equipment company, Jordan, MN) by means of a screw feeder.
To pre-wet the mixture, about 22 pounds per minute or 4.6% water was added. The water was dispersed into the calcium sulfate hemihydrate and bisulfate throughout the Scott mixer. The pre-wetted stucco and additive mixture was transported from the outlet of the Scott mixer to a plate mixer by a conveyor. About 3 minutes was required from the outlet of the Scott mixer to the inlet plate mixer and the mixture had the opportunity to heal.
Gypsum accelerator was prepared from landplaster (USG, Empire plant) which consists of about 85% calcium sulfate dihydrate and 15% impurities. The grinding of the landplaster and the sugar is carried out in a ball mill. The gypsum accelerator is then added to the board mixer at a rate of about 17 pounds per thousand square feet of wallboard. 1135 pounds of water was added to the wet calcium sulfate and bisulfate mixture from the Scott mixer, the gypsum accelerator and the main feed hemihydrate feed stream in a board mixer to form a slurry.
Gypsum board products are prepared from the gypsum slurry. At the point where the board was cut, the hydration of the board with the addition of sodium bisulfate and gypsum accelerator was 10% higher than the hydration of the same board without the addition of sodium bisulfate. Water was added to the main mixer constantly throughout the experiment, but an increase in slurry fluidity occurred if a high concentration of bisulfate was added. In addition, the physical properties of the panels show that the compression and nail pull resistance are about the same as for the same panels without added bisulfate.
Examples 7 to 9
In each experiment, 200g of calcium sulfate hemihydrate (USG, Southardplan) was weighed out and set aside. The appropriate amount of sodium bisulfate as shown in table II was weighed. 2g of gypsum accelerator was weighed out for each experiment. The gypsum accelerator is composed of 95% landplaster and 5% sugar, which are ground together. Landplaster (USG, Southard plant) used for accelerator contains 96% dihydrate and 4% impurities. After the sugar and landplaster are ground together, the coated landplaster is heated to about 250 ° F to melt the sugar on the gypsum surface. The gypsum was cooled to room temperature before use. The calcium sulfate hemihydrate, sodium bisulfate and gypsum accelerator powders are mixed together until all components are thoroughly dispersed. 280ml of 67 ° F water was measured and injected into a Waring mixer with high shear blades. The powdered mixture was soaked for 7 seconds and then mixed at high speed for 7 seconds to form a slurry.
Each composition was cast into three cubes. The average weight of the cubes was weighed at the time intervals indicated and the results are shown in table II.
TABLE II
| Fruit of Chinese wolfberry Applying (a) to Example (b) | Sulfuric acid Sodium hydrogen carbonate | Cubic specialWeight in definite time, g | ||||||
| 0 Hour(s) | 2 Hour(s) | 4 Hour(s) | 24 Hour(s) | 50 Hour(s) | 52.5 Hour(s) | 117 Hour(s) | ||
| 7 | 0.0g | 146.57 | 130.03 | 116.94 | 69.20 | 69.23* | 69.27 | 69.24 |
| 8 | 0.2g | 138.37 | 121.66 | 104.11 | 64.61 | 64.63 | 64.63 | 64.66 |
| 9 | 0.4g | 146.55 | 123.13 | 95.96 | 69.02 | 69.03 | 69.00** | 69.03 |
*This value was measured at 48 hours.
**This value was measured at 52.0 hours.
The weight changes over time due to evaporation of water, which can be used to estimate the drying rate for each composition shown in fig. 2. As the amount of bisulfate increases, this results in faster drying times if the amount of gypsum accelerator is maintained at a constant level. Since the amount of water added to each of these samples was constant, the accelerated drying time reflected an improvement in the drying rate.
While particular embodiments of the hydration improvement feature of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes and modifications may be made thereto without departing from the invention in its broader aspects and as set forth in the following claims.
Claims (32)
1. An additive for accelerating the setting reaction of calcium sulfate hemihydrate and water comprising a gypsum accelerator in combination with a bisulfate salt, the gypsum accelerator comprising ground calcium sulfate dihydrate.
2. The additive of claim 1, wherein said gypsum accelerator further comprises a coating agent.
3. The additive of claim 2, wherein the coating agent comprises one of starch, sugar, boric acid, and combinations thereof.
4. The additive of claim 3, wherein said sugar comprises one of dextrose, sucrose and glucose, and combinations thereof.
5. The additive of claim 4, wherein said sugar is fused to the surface of said calcium sulfate dihydrate.
6. The additive of claim 1, wherein said bisulfate salt is one of sodium bisulfate and potassium bisulfate.
7. The additive of claim 6 wherein said bisulfate salt is sodium bisulfate.
8. The additive of claim 4, wherein said sugar is present in an amount of about 5% to about 25% based on the weight of said calcium sulfate dihydrate.
9. A method for accelerating the hardening reaction of calcium sulfate hemihydrate and water comprising:
mixing a gypsum accelerator, a bisulfate salt, calcium sulfate hemihydrate and water to form a slurry, the gypsum accelerator comprising ground calcium sulfate dihydrate;
forming the slurry into a desired shape; and
the slurry is allowed to harden.
10. The method of claim 9, wherein the gypsum accelerator further comprises a coating agent.
11. The method of claim 10, wherein the coating agent comprises one of starch, sugar, boric acid, and combinations thereof.
12. The method of claim 11, wherein the sugar comprises one of dextrose, sucrose, and glucose, and combinations thereof.
13. The method of claim 12, wherein said sugar is melted onto the surface of said calcium sulfate dihydrate.
14. The method of claim 13, wherein the gypsum accelerator comprises from about 5% to about 25% sugar, based on the weight of calcium sulfate dihydrate.
15. The method of claim 14 wherein the gypsum accelerator is present in an amount of from about 3 to about 60 pounds per ton of dry calcium sulfate hemihydrate.
16. The method of claim 9, wherein said bisulfate salt is one of sodium bisulfate and potassium bisulfate.
17. The method of claim 16 wherein said bisulfate salt is sodium bisulfate.
18. The method of claim 15 wherein said bisulfate salt is present in an amount of from about 0.1 to about 10 pounds per ton of dry calcium sulfate hemihydrate.
19. The method of claim 9 further comprising pretreating said bisulfate salt by mixing said bisulfate salt with a portion of said calcium sulfate hemihydrate and wetting said bisulfate salt with a portion of said water and said portion of said calcium sulfate hemihydrate and then mixing said bisulfate salt, said portion of said calcium sulfate hemihydrate and said portion of said water with said gypsum accelerator, the remainder of said calcium sulfate hemihydrate and the remainder of said water.
20. The method of claim 19 wherein said portion of water is from about 1% to about 10% based on the weight of said portion of calcium sulfate hemihydrate.
21. The method of claim 19, wherein the gypsum accelerator further comprises a coating agent comprising one of a starch, a sugar, boric acid, and combinations thereof.
22. A method of making a calcium sulfate product comprising:
adding a first portion of the calcium sulfate hemihydrate to a mixer;
adding a bisulfate salt and a first portion of water to said first portion of calcium sulfate hemihydrate in said mixer in an amount in the range of from about 1% to about 10% based on the weight of said first portion of calcium sulfate hemihydrate;
mixing the bisulfate salt, the first portion of water and the first portion of calcium sulfate hemihydrate in the mixer;
adding the bisulfate salt and the first portion of calcium sulfate hemihydrate pre-wetted with the first portion of water, and a second portion of calcium sulfate hemihydrate and a gypsum accelerator comprising ground calcium sulfate dihydrate to a mixer;
adding a second portion of water to the mixer to form a slurry;
mixing said slurry;
forming the slurry into a desired shape; and
the slurry is allowed to harden.
23. The method of claim 22, wherein the gypsum accelerator further comprises a coating agent.
24. The method of claim 23, wherein the coating agent comprises one of starch, sugar, boric acid, and combinations thereof.
25. The method of claim 24, wherein the sugar comprises one of sucrose, dextrose, and glucose, and combinations thereof.
26. The method of claim 25, wherein said sugar is melted onto the surface of said calcium sulfate dihydrate.
27. The method of claim 22, wherein said bisulfate salt is one of sodium bisulfate and potassium bisulfate.
28. The method of claim 22 wherein said bisulfate salt is sodium bisulfate.
29. The method of claim 24, wherein said sugar is present in an amount of about 5% to about 25% based on the weight of said calcium sulfate dihydrate.
30. The method of claim 22 wherein said bisulfate salt is present in an amount of from about 0.1 to about 10 pounds per ton of calcium sulfate hemihydrate.
31. The method of claim 22 wherein said first portion of water is present in an amount of from about 1% to about 8% by weight of said first portion of calcium sulfate hemihydrate.
32. The process of claim 22 wherein said first portion of water is present in an amount of from about 3% to about 5% based on the weight of said first portion of calcium sulfate hemihydrate.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US09/473,347 US6409823B1 (en) | 1999-12-28 | 1999-12-28 | Hydration enhancing additives |
| US09/473,347 | 1999-12-28 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1341084A true CN1341084A (en) | 2002-03-20 |
| CN1197816C CN1197816C (en) | 2005-04-20 |
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ID=23879175
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB008041709A Expired - Fee Related CN1197816C (en) | 1999-12-28 | 2000-10-13 | Calcined gypsum hydration enhaucing additives |
Country Status (17)
| Country | Link |
|---|---|
| US (1) | US6409823B1 (en) |
| EP (1) | EP1161404B1 (en) |
| JP (1) | JP4780888B2 (en) |
| KR (1) | KR100643218B1 (en) |
| CN (1) | CN1197816C (en) |
| AT (1) | ATE286006T1 (en) |
| AU (1) | AU780883B2 (en) |
| CA (1) | CA2359894C (en) |
| DE (1) | DE60017100T2 (en) |
| DK (1) | DK1161404T3 (en) |
| ES (1) | ES2231278T3 (en) |
| ID (1) | ID29893A (en) |
| MX (1) | MXPA01008506A (en) |
| NO (1) | NO20014154L (en) |
| NZ (1) | NZ513585A (en) |
| PL (1) | PL205963B1 (en) |
| WO (1) | WO2001047828A1 (en) |
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-
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- 2000-10-13 EP EP00973548A patent/EP1161404B1/en not_active Expired - Lifetime
- 2000-10-13 NZ NZ513585A patent/NZ513585A/en not_active IP Right Cessation
- 2000-10-13 ES ES00973548T patent/ES2231278T3/en not_active Expired - Lifetime
- 2000-10-13 AT AT00973548T patent/ATE286006T1/en not_active IP Right Cessation
- 2000-10-13 JP JP2001549306A patent/JP4780888B2/en not_active Expired - Fee Related
- 2000-10-13 MX MXPA01008506A patent/MXPA01008506A/en active IP Right Grant
- 2000-10-13 PL PL349604A patent/PL205963B1/en not_active IP Right Cessation
- 2000-10-13 WO PCT/US2000/028487 patent/WO2001047828A1/en active IP Right Grant
- 2000-10-13 DE DE60017100T patent/DE60017100T2/en not_active Expired - Lifetime
- 2000-10-13 CN CNB008041709A patent/CN1197816C/en not_active Expired - Fee Related
- 2000-10-13 AU AU12048/01A patent/AU780883B2/en not_active Ceased
- 2000-10-13 DK DK00973548T patent/DK1161404T3/en active
- 2000-10-13 KR KR1020017010618A patent/KR100643218B1/en not_active IP Right Cessation
- 2000-10-13 ID IDW00200101839A patent/ID29893A/en unknown
- 2000-10-13 CA CA2359894A patent/CA2359894C/en not_active Expired - Fee Related
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| CN108439846A (en) * | 2018-01-22 | 2018-08-24 | 曲靖师范学院 | One kind accelerating hydration sunset yellow coagulant for β semi-hydrated gypsums |
| CN110759659A (en) * | 2018-07-27 | 2020-02-07 | 北新集团建材股份有限公司 | Coagulant and preparation method and application thereof |
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Also Published As
| Publication number | Publication date |
|---|---|
| WO2001047828A1 (en) | 2001-07-05 |
| JP2003519070A (en) | 2003-06-17 |
| DE60017100D1 (en) | 2005-02-03 |
| NZ513585A (en) | 2001-09-28 |
| AU1204801A (en) | 2001-07-09 |
| US6409823B1 (en) | 2002-06-25 |
| CA2359894A1 (en) | 2001-07-05 |
| ATE286006T1 (en) | 2005-01-15 |
| ES2231278T3 (en) | 2005-05-16 |
| CN1197816C (en) | 2005-04-20 |
| PL205963B1 (en) | 2010-06-30 |
| EP1161404A1 (en) | 2001-12-12 |
| KR100643218B1 (en) | 2006-11-10 |
| EP1161404B1 (en) | 2004-12-29 |
| ID29893A (en) | 2001-10-18 |
| NO20014154D0 (en) | 2001-08-27 |
| CA2359894C (en) | 2010-01-26 |
| KR20020004951A (en) | 2002-01-16 |
| NO20014154L (en) | 2001-08-27 |
| AU780883B2 (en) | 2005-04-21 |
| DE60017100T2 (en) | 2005-06-02 |
| DK1161404T3 (en) | 2005-02-07 |
| JP4780888B2 (en) | 2011-09-28 |
| MXPA01008506A (en) | 2002-06-21 |
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